River recharge project officially unveiled

The official opening of the Waikirikiri / Selwyn Near River Recharge site in September marks an important point in the fight to improve freshwater ecosystem health in the catchment.

Representatives from Environment Canterbury, Taumutu Rūnanga, Selwyn Waihora Water Zone Committee, Central Plains Water, Department of Conservation, project contractors, and the Selwyn District Council joined project leaders and students from Greendale School to mark the official opening of the project – even if it wasn’t in operation.

Officially open – but still dry

Recent weather patterns have brought rain to the Selwyn foothills, which meant the Waikirikiri / Selwyn River has been flowing near the recharge site.

This means, in essence, that the river is “doing its job,” flowing downstream and recharging groundwater without the need for targeted stream augmentation.

However, this won’t always be the case; changing climate patterns are likely to bring longer dry spells to the Canterbury plains and foothills.

A large-scale solution

The scheme is believed to be the largest Near River Recharge project in the world specifically focused on environmental, cultural and recreational objectives.

Those objectives are to protect the many cultural, environmental and recreational values the river system supports.

The 10-year, multi-million-dollar project is a key aspect in the Canterbury Water Management Strategy.

It was recommended by the Selwyn Waihora Water Zone Committee and included in their Zone Implementation Programme Addendum (ZIPA) in 2013.

The Near River Recharge project cost around $2.8 million dollars, funded by Environment Canterbury and the Ministry for the Environment’s Freshwater Improvement Fund, with Central Plains Water providing in-kind support.

Helping the river do its job

The project uses up to 3.5 cumecs (that’s 3500 litres a second) of water taken from a high-pressure pipe carrying water from the Rakaia through the Central Plains Water scheme, which passes the site.

Central Plains has a consent to take this water from the Rakaia, but only when it meets minimum flow conditions.

It enters a valve house where the water is slowed down before being discharged it into a large – and leaky – basin.

An overflow channel is located at the far end of the basin.

From the basin and overflow channel, the water percolates into the groundwater system, recharging the aquifer and eventually reappearing in the springs in the lower Hororata River – home to the endangered kōwaro / Canterbury mudfish – and the lower Waikirikiri / Selwyn River, enhancing flow at the Chamberlains Ford and Coes Ford recreation areas.

In this way, the project mimics and enhances the effect of the river itself, which naturally runs dry as it loses its flow to groundwater.

Planted seedlings

Native seedlings have been planted around the recharge basin.

Supporting the environment and education

The site is surrounded by pine plantation, providing some shelter.

Hundreds of native seedlings, including tōtara, have been planted around the basin, which in time will provide habitat for native birds.

Rock piles located around the site have created an ideal lizard habitat.

Students at nearby Greendale School have adopted the site as a Living Laboratory through the Enviroschools programme.

The students have been studying river recharge, predator management, native species and their habitats, and the site provides an ideal space for them to see conservation in action.